The objectives of this study are: to evaluate the safety and antiviral activity of monotherapy with ABT-538 at a dose of 600 mg bid, monotherapy with ZDV at a dose of 200 mg tid and combination therapy with ABT-538 and ZDV in HIV infected patients; and to study the emergence of resistance to ABT-538. This protocol is a double-blind, randomized, three-armed, parallel, multicenter, multicountry, comparative clinical trial. Approximately 360 patients who satisfy the study entry criteria will be enrolled. Enrollment is anticipated to be rapid so that the enrollment period for the study should not exceed three months. To allow investigators flexibility in screening patients, randomization of patients will be permitted at least through May 22, 1995, even if the enrollment target is attained earlier. Approximately 120 patients will be randomized to each of the three treatment arms: ABT-538 at a dose of 600 mg bid, ZDV at a dose of 200 mg tid, and ABT-538 at a dose of 600 mg bid plus ZDV at a dose of 200 mg tid. Prior to starting treatment, baseline evaluations will be done during a one week lead-in period. The preliminary analysis of virological data will be performed after all patients who have been enrolled in the study have completed four months of treatment. A supplemental analysis will be performed after all patients have completed a minimum of eight months of treatment.